The present invention relates to floating apparatus for detecting oil floating on the surface of water and, more particularly, to such an apparatus which has a detecting device comprising electrically conductive, expanded, porous polytetrafluoreothylene (PTFE), or similar material, which absorbs oil thereby causing a change in the electrical conductivity of the material and is detected, and which has a layer of cloth attached to the outer surface of the detecting device resulting in the water level around the detector device being higher than the general surface of the water, whereby the thickness of oil film to which the apparatus responds can be pre-selected.